Energetic Belfast-set comedy-drama “Good Vibrations” pays tribute to real-life record-store owner and amateur impresario Terri Hooley, known among cognoscenti as the godfather of the Belfast punk scene. Like many musical biopics, “Vibrations” dithers between being honest about its hero’s faults (alcoholism, selfishness, being a lousy husband and father) and celebrating his virtues (fearlessness, generosity of spirit). However, the pic’s pluses include a spot-on rendering of the sweaty, shabby period milieu and a breakout turn by thesp Richard Dormer, whose wolfish, charismatic perf as Hooley counts for a lot. Having already toured various fests, the film opens locally in January.

An opening sequence, set winningly to Hank Williams’ “I Saw the Light,” explains how Hooley (played as a moppet by Cathal Maguire) lost an eye in a backyard scuffle. Flash forward to the mid-1970s, when his hometown, Belfast, is being literally ripped apart by sectarian violence.

Hooley (played as an adult by Dormer, best known for his work in legit) has zero interest in getting involved in politics, unlike his socialist father (Karl Johnson). All this happy-go-lucky charmer really cares about is smoking dope and music, particularly the reggae he plays at pub-cum-venue the Harp. It’s here he meets Ruth (Jodie Whittaker, making the most of a thinly written role), a free-spirited English student who soon becomes Hooley’s wife, and later the mother of his child.

Raising coin by secretly mortgaging his and Ruth’s flat, Hooley opens a record store called Good Vibrations, and in the film’s least convincing scene, he persuades the local IRA and Unionist thugs to exempt him from paying protection money or killing him by tapping into their shared love of music.

At a gig for local punk combo Rudi, Hooley has a musical epiphany, and falls in love with the band’s sound and the punk scene’s infectious energy. He sets up a label to record Rudi and his other proteges, the Outcasts, managing both groups. The pic’s emotional highlight tracks Hooley’s alliance with the Undertones, whose single, “Teenage Kicks,” rockets them and Hooley to fame.

Unfortunately, it’s all pretty much downhill from there, both for Hooley’s business enterprises and for the story, which struggles to keep boosting its protagonist’s integrity and his refusal to sell out, even as he alienates friends and family with his near-pathologic fecklessness. Even Dormer’s capacious charm can’t completely compensate for the dreary inevitability of the pic’s all-too-familiar musical-biopic trajectory.

Aging punks themselves and auds in Northern Ireland are likely to feel more indulgent of the film’s flaws. Nevertheless, “Good Vibrations” suffers by comparison with, say, Michael Winterbottom’s more innovative and engaging account of Manchester rock impresario Tony Wilson in “24 Hour Party People,” even though Winterbottom takes an exec producer credit here.